Heat exchanger

ABSTRACT

Heat exchanger ( 1 ) provided with a housing ( 2 ) having a core ( 3 ). The core ( 3 ) comprises a series of plate-shaped fins ( 10 ) placed at least almost parallel to each other, in which each fin ( 10 ) is provided with pipe openings ( 13 ), and bundle of pipes ( 8 ) for passing a first heat exchange medium. Each of the pipes ( 8 ) extends through respective pipe openings ( 13 ) of respective fins ( 10 ). The housing ( 2 ) is provided with an inlet ( 5 ) and an outlet ( 7 ) for passing a second heat exchange medium through the housing ( 2 ). At least one of the fins ( 10 ) is further provided with mix openings ( 20 ). Preferably at least one of the fins ( 10 ) is further provided with local elevations ( 23 ). Preferably between the core ( 3 ) and the housing ( 2 ) a strip ( 14 ), preferably of springy material, has been arranged for reducing leakage between the core ( 3 ) and the housing ( 2 ).

[0001] The present invention relates to a heat exchanger provided with ahousing having a core, comprising a series of plate-shaped fins placedat least almost parallel to each other, in which each fin is providedwith pipe openings, and a bundle of pipes for passing a first heatexchange medium, in which each of the pipes extends through respectivepipe openings of respective fins, in which the housing is provided withan inlet and an outlet for passing a second heat exchange medium throughthe housing.

[0002] Such a heat exchanger is known from Dutch patent application9500633. Although the known heat exchanger functions well, theefficiency of the heat exchanger may not be optimal depending on thesecond heat exchange medium. For instance when the heat exchanger isused as oil cooler, so in cases in which the second heat exchange mediumis oil, the oil can supposedly “freeze to” the plate-shaped fins and thepipes, which have a lower temperature than the oil. This means that oilflowing between the fins and pipes does not optimally contact the finsand the pipes because a layer of oil is “frozen” on them. The degree of“freezing” strongly depends on the kind of second heat exchange medium,but causes a blockage for the second heat exchange medium, which leadsto a high drop in pressure and a low heat exchange.

[0003] It is amongst others an objective of the present invention toprovide a heat exchanger with which an improved efficiency of the heatexchange can be obtained. It is noted here that a heat exchanger is notonly suitable to be used as oil cooler for for instance generators,motors and the like, but that the heat exchanger may for instance alsobe used for indeed heating the second heat exchange medium.

[0004] To that end a heat exchanger of the kind described aboveaccording to the present invention is characterized in that at least oneof the fins is further provided with mix openings. Because the secondheat exchange medium during use flows past the mix openings, said flowin comparison to the flow over the locations of the fins where no mixopenings have been arranged, is disturbed such that the flow can reachthe plate-shaped fins and the pipes, thus improving the efficiency ofthe heat exchanger. So although the arranging of mix openings reducesthe effective surface of the fins, and therefore a lower efficiencywould be expected, it appears that the efficiency is indeed improved.

[0005] When the mix openings are placed there where a rate of flow ofthe second heat exchange medium is high in comparison to the rate offlow on other locations, a further improvement of the efficiency isachieved. Preferably the pipe openings are situated in rows next to eachother. In particular each of the mix openings are situated betweenrespective adjacent pipe openings.

[0006] Although between two adjacent pipe openings one mix opening canbe arranged, it is preferred in a heat exchanger, in which the centresof two adjacent pipe openings are connected to each other by animaginary connecting line, that two mix openings are placed on eitherside at equal distance from the connecting line. As a result theefficiency of the heat exchanger is further improved.

[0007] The mix openings may have different shapes, but depending on thesecond heat exchange medium it is preferred that the mix openings aresemi-circular, circular or oval.

[0008] Preferably around a mix opening the respective plate-shaped finis provided with a torsion. As a result the disturbance of the flow ofthe second heat exchange medium is further increased, as a result ofwhich the efficiency is even further improved. Although any givendisturbance results in improvements, it is preferred that the torsion issuch that a flow of second heat exchange medium is directed at a pipeand to a plate-shaped fin, respectively. As a result it is ensured thatthe “frozen” layer of second heat exchange medium on the pipe and thefins is accurately broken through.

[0009] A further disturbance of the flow, which benefits the efficiency,is provided because at least one of the fins is further provided withlocal elevations. Preferably at least one of the elevations is providedwith a groove, which is able to give a certain direction to thedisturbance. Said direction may be adjusted depending on the wantedeffect and the second heat exchange medium.

[0010] An improved distribution of the second heat exchange medium, andthus an improved efficiency is achieved because several fins areprovided with mix openings, and because the heat exchange is furtherprovided with one thread which extends through respective openings ofrespective fins. Preferably the thread is located near thecircumferential edge of the respective fins.

[0011] For reducing the leakage, for instance oil leakage, between thehousing and the core a strip has been arranged between the core and thehousing. Preferably the strip is made of springy material. Because ofthe strip the leakage length of the second head exchange medium isincreased. Moreover the strip may be of such a shape that the path thesecond heat exchange medium has to traverse is complicated, so that theleakage resistance is increased. Said strip also gives plate-shaped finswithout mix openings a good leakage reduction. This is contrary to Dutchpatent application 9500633, in which between the housing and the core asleeve is arranged.

[0012] Some embodiments of a heat exchanger and tin according to thepresent invention will by way of example be described on the basis ofthe drawing.

[0013]FIG. 1 schematically shows a longitudinal cross-section of a heatexchanger according to the invention,

[0014]FIG. 2 schematically shows a top view of a part of a fin accordingto the present invention, to be used in a heat exchanger according tothe present invention,

[0015]FIGS. 3 and 4 schematically show the torsion of a fin aroundrespective mix openings,

[0016]FIGS. 5A and 5B schematically show alternative embodiments of alocal elevation in a fin in cross-section, and

[0017]FIGS. 6 and 7 show a cross-section and a view, respectively, of astrip for reducing leakage between housing and core.

[0018] The heat exchanger 1 as shown in the drawing comprises asubstantially cylindrical housing 2 having a core 3 accommodated inthere. At the top side near a first end 4, the housing 2 has an inlet 5and at the opposite side 6 an outlet 7. The inlet 5 and the outlet 7 canbe connected to a supply and return lead for a second heat exchangemedium, for instance oil to be cooled. During use, apart from the inlet5 and outlet 7, the housing 2 with the core 3 accommodated in there isentirely enclosed, and the oil can be led through the housing under highpressure. The inlet and the outlet may for that matter also bedifferently positioned and several inlets and/or outlets may bearranged.

[0019] The core 3 comprises a bundle of pipes 8 extending almostparallel to each other and in longitudinal direction of the housing 2.On both ends of the core 3 an end plate 9 has been arranged which canfittingly be accommodated in or against the housing 2. The pipes 8extend through the end plates, as a result of which the ends of thepipes are open and may be connected to a supply and discharge,respectively, of a first heat exchange medium, for instance water oranother cooling fluid. Between the end plates 9 a large number of fins10 have been arranged which extend almost parallel to the end plates andto each other, through which fins the pipes extend. The fins 10therefore extend almost at right angles to the longitudinal direction ofthe pipes 8 contact each other closely, for instance because the pipes 8are somewhat flared within the fins 10, as a result of which good heatconductance between the fins 10 and the pipes 8 is guaranteed. The fins10 and the pipes 8 may of course for that matter also be connected oneto the other in a conducting manner in other ways.

[0020] The fins 10 are all almost identical and are made of relativelythin plate. Each fin 10 has an almost circular cross-section withflattened top side 11 and a bottom side 12. Over the surface a number ofholes 13 corresponding to the number of pipes has been arranged in aregular distribution, through which holes the pipes 8 can be arranged.For simple assembly the holes 13 are a little larger that thecross-section of the pipes 8 in the outlet shape.

[0021] Around the core and between the end plates 9 a strip 14 (seeFIGS. 6 and 7) has been arranged. The strip 14 increases the leakageresistance for oil, so that a considerable reduction of oil leakagearises. In particular the strip 14 is made of springy material so that agood fitting in realised. A good fitting in a certain housing may alsobe obtained by correct dimensioning of the strip. The reduction ofleakage is also obtained with plate-shaped fins without mix openings. Asa result of correct design of the strip, for instance a shown in FIG. 6,leakage resistance may further be increased.

[0022]FIG. 2 schematically shows a top view of a part of a fin 10according to the present invention, to be used in a heat exchangeraccording to the present invention. The fin 10 is further provided withmix openings 20. Because the second heat exchange medium for instanceoil, during use flows past the mix openings 20, said flow in comparisonwith the flow over places of the fin 10 where no mix openings 20 havebeen arranged, will be distributed such that the flow can reach thepipes 8 or the adjacent fins, thus improving the efficiency of the heatexchanger.

[0023] Although the mix openings 20 can be arranged on various places onthe fin 10, it is preferred that the mix openings 20 are placed therewhere a rate of flow of the second heat exchange medium is high incomparison to the rate of flow on other locations. The highest rate offlow appears to be present between two adjacent pipes, so thatpreferably each of the mix openings 20 is situated between respectiveadjacent pipe openings 13, as shown in FIG. 2.

[0024] In the example shown centres 30, 31 of two adjacent pipe openings13 may be connected by an imaginary connecting line 32. Two mix openings20 ₁ and 20 ₂ are placed on either side at equal distance from theconnecting line 32, so that a considerable improvement of the efficiencyof the heat exchanger is obtained.

[0025] Although in the show exemplary embodiment the mix openings aresubstantially circular, other shapes may be suitable depending on thekind of second heat exchange medium. Semi-circular and oval mix openingsshould particularly be kept in mind here.

[0026] Preferably around a mix opening 20 ₃ and 20 ₄ the respectiveplate-shaped fin 10 is provided with a torsion. Because of such atorsion the flow of the second heat exchange medium is further disturbedas a result of which the efficiency of the heat exchange is furtherimproved. Although any given disturbance will result in improvements,excellent results can be obtained when the torsion in such that a flowof second heat exchange medium is directed to a pipe 8 or an adjacentplate-shaped fin. An attempt to show said torsion in a drawing, is madein FIGS. 3 to 4. In FIG. 3 a channel through the area between the pipeopenings 13 is indicated, through which channel the flow takes place.The triangular area 22 (FIG. 2) indicates a local bulge as a result fromthe torsion which causes further efficiency-improving disturbance of theflow. In FIGS. 3 and 4 the torsion of the fin 10 is schematically shownby the waviness. By directing the flow to the pipe 8 or an adjacent fin,it is ensured that the “frozen” layer of second heat exchange medium isaccurately broken through.

[0027] Furthermore the fin 10 may be provided with local elevations 23,23′ (see FIG. 2, and FIGS. 5A and 5B). Preferably the elevation 23, 23′is provided with a groove 24, 24′ which can give a certain direction tothe disturbance. Said direction can be adjusted depending on the wantedeffect and the second heat exchange medium. In the example shown thedirection is approximately 45° with respect to the general flowdirection, indicated by arrow S.

[0028] An improved distribution of the second heat exchange medium, andas a result an improved efficiency apparently can be obtained whenseveral fins 10 are provided with mix openings 20 (FIG. 1), and that theheat exchanger is further provided with at least one thread 25,extending through respective mix openings 20 of respective fins 10. Thelargest effect is achieved when the thread 25 is situated near thecircumferential edge of the respective fins 10, in other words when thethread is situated as close to the housing as possible.

[0029] In the heat exchanger known from NL-A-9500633 the distancebetween the fins is several mm. Reducing said distance is not possiblethere, because as a result larger laminar flow between the fins isgenerated, which would lower the efficiency, because of the fact thatsaid laminar flow would even be less capable to contact the pipes in aheat exchanging manner. According to the invention it is possible,however, to reduce this distance in a range of 0.5 mm to 2.0 mm, forinstance 0.6 mm, 0.8 mm or 1.1 mm, which in practice is easy to realize.As a result the number of fins per cm is considerably increased whichenlarges the heat exchanging capacity considerably.

[0030] From tests it appeared that a heat exchanger according to thepresent invention was capable of efficiently cool down oil of atemperature of 90° with cooling water of 20° C.

1. Heat exchanger provided with a housing having a core, comprising aseries of plate-shaped fins placed at least almost parallel to eachother, in which each fin is provided with pipe openings, and a bundle ofpipes for passing a first heat exchange medium, in which each of thepipes extends through respective pipe openings of respective fins, inwhich the housing is provided with an inlet and an outlet for passing asecond heat exchange medium through the housing, which flows between thefins according to a flow direction, characterized in that at least oneof the plate-shaped fins is provided with cut out mix openings, whereinthe respective plate-shaped fin is provided with a torsion to both sidesof the around said mix openings.
 2. heat exchanger according to claim 1,wherein the torsion is in a plane perpendicular to the flow direction ofthe second heat exchange medium.
 3. Heat exchanger according to claim 1or 2, characterized in that the mix openings are placed there where arate of flow of the second heat exchange medium is high in comparison tothe rate of flow on other locations.
 4. Heat exchanger according toclaim 1, 2 or 3, characterized in that the pipe openings are situated inrows next to each other, said rows extending perpendicular to the flowdirection of the second heat exchange medium, wherein each of the mixopenings is situated between respective adjacent pipe openings.
 5. Heatexchanger according to claim 4, in which the centres of two adjacentpipe openings are connected to each other by an imaginary connectingline, wherein two mix openings are placed on either side at equaldistance from the connecting line.
 6. Heat exchanger according to claim5, wherein adjacent pipe opening rows are offset with respect to eachother over half a pipe distance perpendicular to the flow direction ofthe second heat exchange medium.
 7. Heat exchanger according to any oneof the preceding claims, characterized in that the torsion is such thata flow of second heat exchange medium is directed at a pipe and to aplate-shaped fin, respectively.
 8. Heat exchanger according to any oneof the preceding claims, characterized in that the mix openings aresemi-circular.
 9. Heat exchanger according to any of the claims 1-7,characterized in that the mix openings are circular.
 10. Heat exchangeraccording to any of the claims 1-7, characterized in that the mixopenings are oval.
 11. Heat exchanger according to any one of thepreceding claims, characterized in that at least one of the fins isfurther provided with local elevations.
 12. Heat exchanger according toclaim 11, characterized in that at least one of the elevations isprovided with a groove.
 13. Heat exchanger according to any one of thepreceding claims, characterized in that the distance between twoadjacent fins is within a range of 0.5 and 2.0 mm.
 14. Plate-shaped finto be used in a heat exchanger according to any one of the precedingclaims.
 15. Heat exchanger according to any one of the preceding claims,characterized in that several fins are provided with mix openings, andin that the heat exchanger is further provided with at least one threadwhich extends through respective openings of respective fins.
 16. Heatexchanger according to claim 15, in which each respective fin has acircumferential edge, in which the thread is located near thecircumferential edge.
 17. Heat exchanger according to any one of thepreceding claims, characterized in that between the core and the housinga strip has been arranged for reducing leakage between the core and thehousing.
 18. Heat exchanger according to claim 17, characterized in thatthe strip is of a springy material.
 19. Heat exchanger provided with ahousing having a core, comprising a series of plate-shaped fins placedat least almost parallel to each other, in which each fin is providedwith pipe openings, and a bundle of pipes for passing a first heatexchange medium, in which each of the pipes extends through respectivepipe openings of respective fins, in which the housing is provided withan inlet and an outlet for passing a second heat exchange medium throughthe housing, characterized in that between the core and the housing astrip has been arranged for reducing leakage between the core and thehousing.
 20. Heat exchanger according to claim 19, characterized in thatthe strip is of a springy material.